Method for producing a semifinished product for an optical component of high homogeneity

Abstract

Known methods for producing a semifinished product for an optical component of synthetic quartz glass of high homogeneity require a great number of forming or shaping steps for homogenization, which is troublesome in terms of energy and time and entails the risk that impurities might be introduced. To avoid these drawbacks, a method modification is suggested that comprises the following method steps: (a) feeding a silicon-containing start compound, which can be converted by oxidation or hydrolysis into SiO 2 , to a deposition burner, and forming amorphous SiO 2 particles in a burner flame assigned to the deposition burner, (b) forming a substantially solid-cylinder SiO 2 blank by depositing the SiO 2 particles onto a support with a longitudinal axis by way of successive layers, of which most extend in parallel with the longitudinal axis of the support and which extend in the direction of the outer surface of the blank, (c) homogenizing the SiO 2 blank, including twisting along an axis of rotation extending coaxially to or in parallel with the longitudinal cylinder axis while forming the semifinished product. A blank suited for performing the method of the invention and shaped in the form of a substantially solid-cylinder SiO 2 soot body from successive SiO 2 layers is characterized in that most of the layers extend in parallel with the longitudinal axis of the soot body and in the direction of the outer surface of the soot body.

1. A method for producing a semifinished product for an optical component of synthetic quartz glass of high homogeneity, the method comprising:
 (a) feeding a silicon-containing start compound, which can be converted by oxidation or hydrolysis into SiO 2 , to a deposition burner, and forming amorphous SiO 2  particles in a burner flame associated with the deposition burner; 
 (b) forming a substantially solid-cylinder SiO 2  blank by depositing the SiO 2  particles onto a support with a longitudinal axis in successive layers, most of said layers extending in parallel with the longitudinal axis of the support and extending toward and ending at an outer cylindrical surface of the blank; and 
 (c) homogenizing the SiO 2  blank, including twisting along an axis of rotation extending coaxially to or in parallel with the longitudinal axis while forming the semifinished product. 
 
     
     
       2. The method according to  claim 1 , wherein most of the layers terminate at the outer cylindrical surface of the blank and define an angle between an end thereof facing the outer surface and said outer surface, said angle being between 10° and 170°. 
     
     
       3. The method according to  claim 2 , wherein the angle is between 30° and 150°. 
     
     
       4. The method according to  claim 2 , wherein the angle is between 60° and 120°. 
     
     
       5. The method according to  claim 1 , wherein a relative movement is produced between the burner flame and the support, the relative movement having a first component in the direction of the longitudinal axis of the support and a second component in a direction perpendicular to said longitudinal axis. 
     
     
       6. The method according to  claim 1  wherein most of the layers are substantially planar and extend in parallel with one another. 
     
     
       7. The method according to  claim 1 , wherein most of the layers have curved areas. 
     
     
       8. The method according to  claim 1 , wherein the support has a recess therein extending along the longitudinal axis so as to receive the SiO 2  particles. 
     
     
       9. The method according to  claim 8 , wherein a deposition surface within the recess is shaped in the form of a half shell. 
     
     
       10. The method according to  claim 1  wherein the SiO 2  blank of method step (b) is a porous SiO 2  soot body, and prior to the homogenization of method step (c), the soot body is sintered to obtain a transparent blank. 
     
     
       11. The method according to  claim 10 , wherein the SiO 2  soot body has a low mean density in a range between 0.22 g/cm 3  and 0.55 g/cm 3 . 
     
     
       12. The method according to  claim 11 , wherein the soot body of low mean density is subjected to a pre-sintering process prior to sintering in which the mean density thereof is set to more than 0.55 g/cm 3 . 
     
     
       13. The method according to  claim 12 , wherein the mean density is set to at least 0.77 g/cm 3 . 
     
     
       14. The method according to  claim 11  wherein the SiO 2  soot body has a mean density in a range between 0.30 g/cm 3  and 0.50 g/cm 3 . 
     
     
       15. The method according to  claim 10 , wherein, prior to sintering, the soot body is treated in a horizontally lying position in a drying atmosphere. 
     
     
       16. The method according to  claim 1 , wherein the SiO 2  blank has a first end and a second end opposite to said first end in a direction of a central axis of the blank, and wherein during deposition of the SiO 2  particles a holder is embedded into the first end of the blank, said holder extending beyond the end of the blank in the central axis of the blank. 
     
     
       17. A method for producing a semifinished product for an optical component of synthetic quartz glass of high homogeneity, the method comprising:
 (a) feeding a silicon-containing start compound, which can be converted by oxidation or hydrolysis into SiO 2 , to a deposition burner, and forming amorphous SiO 2  particles in a burner flame associated with the deposition burner; 
 (b) forming a substantially solid-cylinder SiO 2  blank by depositing the SiO 2  particles onto a support with a longitudinal axis in successive layers that extend in parallel with the longitudinal axis of the support, and extend toward and end at an outer cylindrical surface of the blank; and 
 (c) homogenizing the SiO 2  blank, including twisting along an axis of rotation extending coaxially to or in parallel with the longitudinal axis while forming the semifinished product. 
 
     
     
       18. The method according to  claim 17 , wherein the layers terminate terminate at the outer cylindrical surface of the blank and define an angle between an end thereof facing the outer surface and said outer surface, said angle being between 10° and 170°. 
     
     
       19. The method according to  claim 17  wherein the layers are substantially planar and extend in parallel with one another. 
     
     
       20. The method according to  claim 17  wherein the layers have curved areas. 
     
     
       21. The method according to  claim 17 , wherein the layers terminate terminate at the outer cylindrical surface of the blank and define an angle between an end thereof facing the outer surface and said outer surface, said angle being between 30° and 150°. 
     
     
       22. The method according to  claim 17 , wherein the layers terminate terminate at the outer cylindrical surface of the blank and define an angle between an end thereof facing the outer surface and said outer surface, said angle being between 60° and 120°.